The acrosome reaction must occur for sperm to penetrate the investments surrounding the ovum and ultimately for fertilization to take place. It is believed that the acrosome reaction releases various hydrolytic enzymes needed for its penetration of the ovum. Thus, if these acrosomal enzymes are to avoid dilution in the reproductive tract the time of the acrosome reaction must be controlled. This proposal suggests that control of the acrosome reaction can be attributed to an acrosome stabilizing factor, present in the ejaculated sperm, and an acrosome reaction inducer, in the products of ovulation. The Acrosome Stabilizing Factor (ASF) has been purified to homogeneity in this lab and it is proposed to: 1) study ASF sperm interaction by fluorescent localization 2) develop an RIA for ASF and 3) use the RIA to define factors involved in ASF sperm interactions at the molecular level. Further, this proposal seeks to define the product of ovulation which induces the acrosome reaction. Does enough follicular fluid get into the oviduct? Attempts will also be made to evaluate the in vivo role of immunological complement on inducing the acrosome reaction.